It’s nitpicking, but Matt Harvey has room for improvement on what has been a spectacular body of work to start the season, according to catcher John Buck.

When the Mets’ phenom takes his 4-0 record and 0.93 ERA to the mound against the Dodgers tonight, Buck wants Harvey to reduce the number of overthrown pitches he unleashes. Buck says Harvey has averaged about 10 overthrown pitches in his first four starts.

“Every once in a while he’ll overthrow his fastball or he’ll yank his slider too much or he throws too hard where he backs it up,” Buck said yesterday. “It’s still nasty, but sometimes he will overthrow it and not get the break that’s the real nasty stuff.”

By executing better on just a few pitches per game, Buck said it could allow Harvey to extend his starts by an extra inning, because hitters will presumably be putting the ball in play earlier in the count.

Buck says he has already had that discussion with the 24-year-old fireballer.

In his last start, Harvey allowed one run over seven innings to top Nationals ace Stephen Strasburg.

* Aaron Laffey, whom the Mets designated for assignment on Sunday, was claimed off waivers by the Blue Jays. The lefty pitched last season with Toronto before signing a minor league deal with the Mets.

* Shaun Marcum was expected to arrive in New York yesterday and is expected to make his Mets debut on Saturday against the Phillies. The veteran right-hander threw five scoreless innings in a simulated game on Monday in Port St. Lucie.

* Ike Davis was on the bench against Dodgers ace Clayton Kershaw, giving Justin Turner a start at first base. Collins said he isn’t tempted to move Lucas Duda to first base on days Davis doesn’t play.

“Lucas has played pretty well in left field right now,” Collins said. “If I go to him and say, ‘You need to start taking ground balls at first base,’ I’m not sure what kind of message that sends. One of the things I want to have this kid do when he takes the field each day is be comfortable out there.”